The serial default address is 69h, you will need a unique address for each device. You can program using the I2C bus, however, it will only program the volatile side. The reason the devices need to be off the PCB is because you have to program the EEPROM for the non-volatile registers. You can also change the default address through CyberClocks. The non-volatile registers in these devices can be programmed using the CY3672-USB programmer or those from other Cypress-qualified vendors. There is no limit on how many times the volatile registers can be programmed via the serial programming interface, which is I2C compatible.